In MARK-SPACE digital tank gauging systems for monitoring liquid level, conductor buses directly connect all tank stations with a central control monitoring location. Individual tank stations are in multiplexed circuit connection with the central monitoring location. During operations, line voltage of the conductor buses must be held at rather high levels, say 48 volts, to avoid accidental tripping of the system by natural phenomenon, such as lighting. In order to create a MARK or SPACE on the lines of interest, the transducer system associated therewith must generate a complementary high level signal. However, experience has shown that to generate such signals by solid state circuitry say essentially MSI's (Medium Scale Integrated Chips) where such circuits must be formed with minimum device count, simple control capability and low power requirements, is exceedingly difficult to accomplish. This is especially true if the circuit must also be interfaced with present on-site tank gauging systems.
Moreover, there is a present need for an accurate transducer system for monitoring fluid levels within oil refineries and/or chemical complexes, such need having been brought about, to a large extent, by changes in Federal and State laws. While normal refinery practice seeks to avoid overloading storage tanks, now penalties provided by Federal and State laws are so severe, that highly accurate monitoring systems are mandatory. However, experience shows that such systems are difficult to achieve because the reasons previously mentioned, especially if a separate analog-to-BCD-to-Gray code convertors, are to be used.